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/// Query Engine Demo
///
/// Demonstrates SQL-like query capabilities in RustLite v0.4.0+
use rustlite::{Column, Database, ExecutionContext, Row, Value};
fn main() -> Result<(), Box<dyn std::error::Error>> {
println!("=== RustLite v0.4.0 Query Engine Demo ===\n");
// Create an in-memory database
let db = Database::in_memory()?;
// Prepare sample data
let mut context = ExecutionContext::new();
// Sample users table
context.data.insert(
"users".to_string(),
vec![
Row {
columns: vec![
Column {
name: "id".to_string(),
alias: None,
},
Column {
name: "name".to_string(),
alias: None,
},
Column {
name: "age".to_string(),
alias: None,
},
Column {
name: "city".to_string(),
alias: None,
},
],
values: vec![
Value::Integer(1),
Value::String("Alice".to_string()),
Value::Integer(30),
Value::String("NYC".to_string()),
],
},
Row {
columns: vec![
Column {
name: "id".to_string(),
alias: None,
},
Column {
name: "name".to_string(),
alias: None,
},
Column {
name: "age".to_string(),
alias: None,
},
Column {
name: "city".to_string(),
alias: None,
},
],
values: vec![
Value::Integer(2),
Value::String("Bob".to_string()),
Value::Integer(25),
Value::String("SF".to_string()),
],
},
Row {
columns: vec![
Column {
name: "id".to_string(),
alias: None,
},
Column {
name: "name".to_string(),
alias: None,
},
Column {
name: "age".to_string(),
alias: None,
},
Column {
name: "city".to_string(),
alias: None,
},
],
values: vec![
Value::Integer(3),
Value::String("Charlie".to_string()),
Value::Integer(35),
Value::String("NYC".to_string()),
],
},
Row {
columns: vec![
Column {
name: "id".to_string(),
alias: None,
},
Column {
name: "name".to_string(),
alias: None,
},
Column {
name: "age".to_string(),
alias: None,
},
Column {
name: "city".to_string(),
alias: None,
},
],
values: vec![
Value::Integer(4),
Value::String("Diana".to_string()),
Value::Integer(28),
Value::String("LA".to_string()),
],
},
],
);
// Example 1: Simple SELECT *
println!("1. SELECT * FROM users");
let results = db.query("SELECT * FROM users", context.clone())?;
print_results(&results);
// Example 2: SELECT with WHERE clause
println!("\n2. SELECT name, age FROM users WHERE age > 28");
let results = db.query(
"SELECT name, age FROM users WHERE age > 28",
context.clone(),
)?;
print_results(&results);
// Example 3: SELECT with ORDER BY
println!("\n3. SELECT name, age FROM users ORDER BY age DESC");
let results = db.query(
"SELECT name, age FROM users ORDER BY age DESC",
context.clone(),
)?;
print_results(&results);
// Example 4: SELECT with LIMIT
println!("\n4. SELECT name FROM users LIMIT 2");
let results = db.query("SELECT name FROM users LIMIT 2", context.clone())?;
print_results(&results);
// Example 5: SELECT with LIMIT and OFFSET
println!("\n5. SELECT name FROM users LIMIT 2 OFFSET 1");
let results = db.query("SELECT name FROM users LIMIT 2 OFFSET 1", context.clone())?;
print_results(&results);
// Example 6: Complex WHERE with AND
println!("\n6. SELECT name, city FROM users WHERE age > 25 AND city = 'NYC'");
let results = db.query(
"SELECT name, city FROM users WHERE age > 25 AND city = 'NYC'",
context.clone(),
)?;
print_results(&results);
// Example 7: Prepared statement
println!("\n7. Using prepared statements");
let plan = db.prepare("SELECT name, age FROM users WHERE age > 26")?;
println!(" Query plan: {}", plan);
let results = db.execute_plan(&plan, context.clone())?;
print_results(&results);
// Example 8: COUNT aggregate
println!("\n8. SELECT COUNT(*) FROM users");
let results = db.query("SELECT COUNT(*) FROM users", context.clone())?;
print_results(&results);
println!("\n=== Query Demo Complete ===");
Ok(())
}
fn print_results(rows: &[Row]) {
if rows.is_empty() {
println!(" No results");
return;
}
// Print header
print!(" ");
for col in &rows[0].columns {
let name = col.alias.as_ref().unwrap_or(&col.name);
print!("{:15} ", name);
}
println!();
print!(" ");
for _ in &rows[0].columns {
print!("{:15} ", "---------------");
}
println!();
// Print rows
for row in rows {
print!(" ");
for val in &row.values {
match val {
Value::Integer(i) => print!("{:<15} ", i),
Value::Float(f) => print!("{:<15.2} ", f),
Value::String(s) => print!("{:<15} ", s),
Value::Boolean(b) => print!("{:<15} ", b),
Value::Null => print!("{:<15} ", "NULL"),
}
}
println!();
}
}